Technology Field
The present disclosure relates to communication devices. More particularly, the present disclosure relates to a portable electronic device and its frequency switching circuit for an antenna.
Description of Related Art
In wireless communication, an antenna of a portable electronic device for transmitting and receiving radio waves is undoubtedly an important component. In recent years, a variety of communications systems and applications are developed, and the antenna is designed toward multi-band for covering a plurality of operating frequency bands.
The conventional multi-band portable electronic device has adjustable antenna architecture capable of adjusting frequency. In one conventional adjustable antenna structure, the antenna and an adjustment means (e.g., switches) are configured to adjust the path to the antenna. However, since the adjustment means is a non-linear element with too large power of the antenna, the adjustment means generates electromagnetic interference (EMI) and therefore causes harmonic distortion to affect the efficiency of the antenna.
In another conventional adjustable antenna structure, the antenna is coupled with a variable capacitance chip to switch the frequency of the antenna by using different capacitance values. However, due to the switching path through the chip, the adjustable antenna with the variable capacitance chip may cause path loss.
In view of the foregoing, there is an urgent need in the related field to achieve requirements of operating bandwidth of the portable electronic device and to extend or adjust the operating bandwidth.